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THE SKELETON  AND   TEETH              147
the writings of Briihl (235:, Bateson {12}, Duckworth (50), Lucas (262), Maggi <26S\ Schmidt and Selenka * 287).
The entire dental series varies considerably with age and sex, and there are probably ruany purely individual variations, so the foregoing account must be regarded a* the average condition. The roots of the teeth are very long.
The upper central incisors are larger than the lateral incisors as in the Orang, but theft crowns are large as in the Gorilla; and the central incisors may be absolutely larger than those in the Gorilla. The canine teeth are tusk-like as in the Orang and Gorilla, and the diastemata are similarly placed.
The enamel of the post-canine teeth is wrinkled and crenated, but it has not got the sharp crystalline form of the enamel in the Gorilla. This character, as Keith (100) points out, lends support to those who separate these Apes into two distinct genera.
The upper premolar teeth, resemble those in Man more than the lower premolars. Both are bicuspid and small. The first has three roots, whereas the second has only two. And there is no sharp difference in size between the second premolar and first molar teeth in the lower jaw.
The upper molar teeth have four cusps, of which the hypocone is large. And the nietacone may be connected to the protocone and hypocone by ridges. The inner root may be divided to a variable extent. The lower molar teeth have five cusps. The third molar tcoth in